1. Technical Field
Various implementations of the disclosed technology relate to flight management systems and control methods and, more particularly, flight management systems and control methods for meeting a required time of arrival with reduced fuel burn. Various implementations of the disclosed technology also relate to systems and methods for modeling wind forecast uncertainty.
2. Description of Related Art
Projected increased traffic loads in the national airspace as well as growing operational inefficiencies have motivated the development of trajectory based operations (TBO), specifically 4-D trajectories (4DT). The inclusion of 4DT-based technologies is meant to mitigate the impact of increased traffic loads on delays, cost of operation, and the environment by improving both an aircraft's ability to meet schedule constraints mid-flight, as well as the ground's ability to foresee and adjust to operational uncertainties.
Current aircraft systems enable 4DT and TBO via the Required Time of Arrival (RTA) mode in the on-board flight management system (FMS). The FMS calculates the control authority required to meet an assigned RTA by considering the distance to the RTA fix, the performance capabilities of the aircraft, and the forecasted wind along the aircraft's route. However, real world uncertainties in the forecasted wind speeds can lead to errors in time-to-fix calculations as forecast error aggregates over the course of the flight. In many cases, flight time prediction accuracy only improves to an acceptable level once the RTA fix is relatively close. By this point, excessive control effort beyond the aircraft's performance capabilities may be required to meet the assigned RTA, leading to increased fuel burn, emissions, and missed RTA assignments.
Conventional FMS RTA technologies lack robustness in two primary areas of operation: fuel expenditure required to meet an assigned RTA, and the ability to calculate a workable control schedule to meet an assigned RTA given known conditions. Both of these shortcomings can be attributed in large part to wind forecast uncertainty along the aircraft's planned route. Conventional FMS RTA technologies typically consider only a deterministic wind speed forecast. As these conventional technologies are unable to account for uncertainty in the forecasted wind speeds, a conventional FMS cannot consider all possible scenarios, including wind scenarios more favorable to the aircraft, in which an FMS can meet an assigned RTA.